Electric potential energy

As electrical energy is called the energy which is transferred by means of the electricity or stored in electric fields. In the transmission of energy by means of electricity is also called electrical work.

In physics, the symbols E and the unit watt second ( unit symbol: Ws) is the electrical energy or joules ( J ) is used. It is 1 Ws = 1 J. In the measurement of energy expenditure in the field of electrical power engineering, the unit is kWh ( kilowatt hour) usual. 1 kWh = 3,600,000 Ws, Ws 1 ≈ 2.778 · 10-7 kWh.

Electrical energy is the most versatile usable energy sources, they can be converted with very small losses in other forms of energy and transport well. Your production and supply of industry and consumers in modern societies of great importance.


The electric power is also referred to as an electric working results from the integral of the product of the electrical voltage and current over time:

For the case of a constant electrical voltage and a constant current there is therefore the electric power from the product of the two values ​​with the time difference ():

Electrical energy can perform like any other energy can not be destroyed or created but is generally converted into a different appearance. By means of conservation of energy, the electrical energy can be determined by calculating the mechanical energy necessary for their generation.

Electric Power

In power plants, batteries and accumulators, electrical energy is transformed from heat energy or chemical energy, for example, transported to consumers through power lines and converted to consumers in other forms of energy ( power, light, heat).

Electric energy can also be stored in the electrostatic field of capacitors. For larger quantities, we used double-layer capacitors. The energy contained in a capacitor is

Wherein the capacitance of the capacitor and the electrical voltage applied to it is.

Magnetic Energy

Magnetic energy manifests itself in a magnetic field and exerts a force on moving charges from, called the Lorentz force. We distinguish electromagnetic and electrodynamic forces. Because of their strength, they are often used in electric motors and generators. Can be stored magnetic energy in everyday life not very durable in a coil or inductor. Superconducting magnetic energy storage on the other hand, a high energy can be stored for a short time.

In an electrical oscillating circuit changes in time with the electric power frequency magnetic energy. The energy contained in a coil is

Where L is the inductance of the coil and I is the electrical current flowing through.

Electrical power in an electric field

If a (sample ) charge moves in an electric field, electric work is done, and there are two signs on the distinguishable directions of movement:

  • Is the direction of movement counter to the force direction of the electric field ( from the outside ), work is carried out, and the potential energy of the charge increases. This process always corresponds to a charge separation.
  • Is the direction of movement on the other hand in the direction of the direction of force of the field, the electric field carries out work on the charge. Free charge carriers are accelerated along the electric field in the conductor to the central drift velocity, and there is a conversion of potential energy into kinetic energy held (see also flexibility ). Overall, therefore, the voltage source (resistance, electric motor) performed in the electrical load and mechanical work produced thereby also always heat ( dissipated work).

The work, as well as other physical work, in watt-seconds (Ws) or joules ( J) specified. The specification in newton meters (N m) would be theoretically possible, but is not to be found in practice.

To move a test charge in an electric field from point to receive ( done ) to electrical work.

Motivated by the definition of mechanical work

Is obtained with the resultant power to a charge Q in the electric field:

The electrical work

The aufintegrierten Wegstückchen are. In a spatially constant field is simply from the integral

The path integral is independent of the path in a conservative electric field, and it can be the voltage ( electric potential ) as

Introduce. This gives the simplified formula


For home use, you need an understanding of electrical work when buying electrical appliances such as a refrigerator or electric lamps. Here it is important to know that the time the device is in operation, the electric power multiplied by the fundamental parameter for calculating the required energy from the electric appliance.

The demand for electrical current in amperes is by design specified by the manufacturer and therefore decides to purchase. The mains voltage in Europe is usually 230 volts and at 400 volts AC, unless one resorts to batteries, batteries or a power supply with low voltage.